Nightcap/ˈnaɪtkæp/ Definition 1 of 2Pro Tip 1/3Informal Relaxation Refers to a comforting routine, suggesting unwinding after a busy day. Join me for a nightcap to relax before we turn in? Pro Tip 2/3Social Gesture Used as a polite offer to extend the evening, conveying hospitality. Before you go, how about a nightcap? Pro Tip 3/3Not Always Alcoholic Can refer to non-alcoholic drinks, emphasizing the purpose of relaxation. I prefer a hot tea as my nightcap.